1. Field of the Invention
The present invention relates to a sensor element for contactlessly measuring a magnetic field in an aggressive environment, in particular for use in a fuel tank of a motor vehicle.
2. Description of the Related Art
From DE 101 42 618 A1 a contactlessly operating level indicator is known which uses a Hall effect sensor as a sensor element for measuring a fill level in a fuel tank, said Hall effect sensor detecting the magnetic field of a magnet. The magnet is connected via a lever with a float such that the measured magnetic field of the magnet varies as a function of the fill level in the fuel tank. The lever is rotatably supported via a rotary axis. The rotary axis is partially embraced by the magnet configured as a ring magnet. The ring magnet is arranged between the Hall effect sensor and the rotary axis. The magnet is disposed in a two-piece housing, wherein the housing halves are closed in a liquid-proof manner by means of cast resin. To protect the Hall effect sensor against the aggressive environment in the fuel tank, the sensor is arranged in a pocket formed in a housing, said pocket also being filled with cast resin.
A drawback of such a sensor element is that considerable constructive efforts are required for protection of the sensor element. It is necessary to use components with complicated geometries which are difficult and expensive to manufacture.
Further, the cast resin does not offer sufficient protection since fuel, which flows along the housing wall thus coming in contact with the cast resin, gradually diffuses through the cast resin such that the sensor element becomes, for example, damaged by corrosion, which results in a relatively short service life of the sensor element.